1The `parport' code provides parallel-port support under Linux. This 2includes the ability to share one port between multiple device 3drivers. 4 5You can pass parameters to the parport code to override its automatic 6detection of your hardware. This is particularly useful if you want 7to use IRQs, since in general these can't be autoprobed successfully. 8By default IRQs are not used even if they _can_ be probed. This is 9because there are a lot of people using the same IRQ for their 10parallel port and a sound card or network card. 11 12The parport code is split into two parts: generic (which deals with 13port-sharing) and architecture-dependent (which deals with actually 14using the port). 15 16 17Parport as modules 18================== 19 20If you load the parport code as a module, say 21 22 # insmod parport 23 24to load the generic parport code. You then must load the 25architecture-dependent code with (for example): 26 27 # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto 28 29to tell the parport code that you want three PC-style ports, one at 300x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an 31auto-detected IRQ. Currently, PC-style (parport_pc), Sun `bpp', 32Amiga, Atari, and MFC3 hardware is supported. 33 34PCI parallel I/O card support comes from parport_pc. Base I/O 35addresses should not be specified for supported PCI cards since they 36are automatically detected. 37 38 39KMod 40---- 41 42If you use kmod, you will find it useful to edit /etc/modprobe.conf. 43Here is an example of the lines that need to be added: 44 45 alias parport_lowlevel parport_pc 46 options parport_pc io=0x378,0x278 irq=7,auto 47 48KMod will then automatically load parport_pc (with the options 49"io=0x378,0x278 irq=7,auto") whenever a parallel port device driver 50(such as lp) is loaded. 51 52Note that these are example lines only! You shouldn't in general need 53to specify any options to parport_pc in order to be able to use a 54parallel port. 55 56 57Parport probe [optional] 58------------- 59 60In 2.2 kernels there was a module called parport_probe, which was used 61for collecting IEEE 1284 device ID information. This has now been 62enhanced and now lives with the IEEE 1284 support. When a parallel 63port is detected, the devices that are connected to it are analysed, 64and information is logged like this: 65 66 parport0: Printer, BJC-210 (Canon) 67 68The probe information is available from files in /proc/sys/dev/parport/. 69 70 71Parport linked into the kernel statically 72========================================= 73 74If you compile the parport code into the kernel, then you can use 75kernel boot parameters to get the same effect. Add something like the 76following to your LILO command line: 77 78 parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo 79 80You can have many `parport=...' statements, one for each port you want 81to add. Adding `parport=0' to the kernel command-line will disable 82parport support entirely. Adding `parport=auto' to the kernel 83command-line will make parport use any IRQ lines or DMA channels that 84it auto-detects. 85 86 87Files in /proc 88============== 89 90If you have configured the /proc filesystem into your kernel, you will 91see a new directory entry: /proc/sys/dev/parport. In there will be a 92directory entry for each parallel port for which parport is 93configured. In each of those directories are a collection of files 94describing that parallel port. 95 96The /proc/sys/dev/parport directory tree looks like: 97 98parport 99|-- default 100| |-- spintime 101| `-- timeslice 102|-- parport0 103| |-- autoprobe 104| |-- autoprobe0 105| |-- autoprobe1 106| |-- autoprobe2 107| |-- autoprobe3 108| |-- devices 109| | |-- active 110| | `-- lp 111| | `-- timeslice 112| |-- base-addr 113| |-- irq 114| |-- dma 115| |-- modes 116| `-- spintime 117`-- parport1 118 |-- autoprobe 119 |-- autoprobe0 120 |-- autoprobe1 121 |-- autoprobe2 122 |-- autoprobe3 123 |-- devices 124 | |-- active 125 | `-- ppa 126 | `-- timeslice 127 |-- base-addr 128 |-- irq 129 |-- dma 130 |-- modes 131 `-- spintime 132 133 134File: Contents: 135 136devices/active A list of the device drivers using that port. A "+" 137 will appear by the name of the device currently using 138 the port (it might not appear against any). The 139 string "none" means that there are no device drivers 140 using that port. 141 142base-addr Parallel port's base address, or addresses if the port 143 has more than one in which case they are separated 144 with tabs. These values might not have any sensible 145 meaning for some ports. 146 147irq Parallel port's IRQ, or -1 if none is being used. 148 149dma Parallel port's DMA channel, or -1 if none is being 150 used. 151 152modes Parallel port's hardware modes, comma-separated, 153 meaning: 154 155 PCSPP PC-style SPP registers are available. 156 TRISTATE Port is bidirectional. 157 COMPAT Hardware acceleration for printers is 158 available and will be used. 159 EPP Hardware acceleration for EPP protocol 160 is available and will be used. 161 ECP Hardware acceleration for ECP protocol 162 is available and will be used. 163 DMA DMA is available and will be used. 164 165 Note that the current implementation will only take 166 advantage of COMPAT and ECP modes if it has an IRQ 167 line to use. 168 169autoprobe Any IEEE-1284 device ID information that has been 170 acquired from the (non-IEEE 1284.3) device. 171 172autoprobe[0-3] IEEE 1284 device ID information retrieved from 173 daisy-chain devices that conform to IEEE 1284.3. 174 175spintime The number of microseconds to busy-loop while waiting 176 for the peripheral to respond. You might find that 177 adjusting this improves performance, depending on your 178 peripherals. This is a port-wide setting, i.e. it 179 applies to all devices on a particular port. 180 181timeslice The number of milliseconds that a device driver is 182 allowed to keep a port claimed for. This is advisory, 183 and driver can ignore it if it must. 184 185default/* The defaults for spintime and timeslice. When a new 186 port is registered, it picks up the default spintime. 187 When a new device is registered, it picks up the 188 default timeslice. 189 190Device drivers 191============== 192 193Once the parport code is initialised, you can attach device drivers to 194specific ports. Normally this happens automatically; if the lp driver 195is loaded it will create one lp device for each port found. You can 196override this, though, by using parameters either when you load the lp 197driver: 198 199 # insmod lp parport=0,2 200 201or on the LILO command line: 202 203 lp=parport0 lp=parport2 204 205Both the above examples would inform lp that you want /dev/lp0 to be 206the first parallel port, and /dev/lp1 to be the _third_ parallel port, 207with no lp device associated with the second port (parport1). Note 208that this is different to the way older kernels worked; there used to 209be a static association between the I/O port address and the device 210name, so /dev/lp0 was always the port at 0x3bc. This is no longer the 211case - if you only have one port, it will default to being /dev/lp0, 212regardless of base address. 213 214Also: 215 216 * If you selected the IEEE 1284 support at compile time, you can say 217 `lp=auto' on the kernel command line, and lp will create devices 218 only for those ports that seem to have printers attached. 219 220 * If you give PLIP the `timid' parameter, either with `plip=timid' on 221 the command line, or with `insmod plip timid=1' when using modules, 222 it will avoid any ports that seem to be in use by other devices. 223 224 * IRQ autoprobing works only for a few port types at the moment. 225 226Reporting printer problems with parport 227======================================= 228 229If you are having problems printing, please go through these steps to 230try to narrow down where the problem area is. 231 232When reporting problems with parport, really you need to give all of 233the messages that parport_pc spits out when it initialises. There are 234several code paths: 235 236o polling 237o interrupt-driven, protocol in software 238o interrupt-driven, protocol in hardware using PIO 239o interrupt-driven, protocol in hardware using DMA 240 241The kernel messages that parport_pc logs give an indication of which 242code path is being used. (They could be a lot better actually..) 243 244For normal printer protocol, having IEEE 1284 modes enabled or not 245should not make a difference. 246 247To turn off the 'protocol in hardware' code paths, disable 248CONFIG_PARPORT_PC_FIFO. Note that when they are enabled they are not 249necessarily _used_; it depends on whether the hardware is available, 250enabled by the BIOS, and detected by the driver. 251 252So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc 253with 'irq=none'. See if printing works then. It really should, 254because this is the simplest code path. 255 256If that works fine, try with 'io=0x378 irq=7' (adjust for your 257hardware), to make it use interrupt-driven in-software protocol. 258 259If _that_ works fine, then one of the hardware modes isn't working 260right. Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option, 261and yes, it should be), set the port to ECP mode in the BIOS and note 262the DMA channel, and try with: 263 264 io=0x378 irq=7 dma=none (for PIO) 265 io=0x378 irq=7 dma=3 (for DMA) 266-- 267philb@gnu.org 268tim@cyberelk.net 269